It is known that cooling rate from the liquid state is an important factor for producing the bulk metallic glasses. However, almost no other factors such as electric and/or magnetic fields were investigated. The present authors have reported that the glass-forming ability of Mg-Cu-Y and Fe-Co-B-Si-Nb alloys is enhanced with increasing electromagnetic vibration force. The electromagnetic vibrations affect the increase of the cooling rate and the decrease in the number of crystal nuclei directly, but don't affect the crystal growing rate. However, effects of the electromagnetic vibrations are not fully investigated so far. Thus, this study aims to investigate effect of the purity and superheating on the glassforming ability of Mg-Cu-Y alloys by the electromagnetic vibration method. It was found that the glass-forming ability of Mg-Cu-Y alloys is sensitive to the purity of an Ar atmosphere under which the mother alloy is prepared. However, the glass-forming ability was enhanced by the electromagnetic vibrations even if the mother alloy was prepared under low purity Ar. The enhancement of the glass-forming ability by the electromagnetic vibrations in the liquid state was decreased with the increase of superheating. These results support the presumption that disappearance or decrement of the clusters by the electromagnetic vibrations applied to the liquid state causes suppression of crystal nucleation.
The method for producing Fe-Co-B-Si-Nb bulk metallic glasses using electromagnetic vibrations is effective in forming the metallic glass phase. The purpose of this study was to investigate the effects of the frequency of electromagnetic vibrations on the vibrational motion in Fe-Co-B-Si-Nb bulk metallic glasses. The amplitudes of the electromagnetic vibrations at 5 kHz were calculated to be on the order of micrometers, but those at higher frequencies were on the order of nanometers. It was found that the nanometer-sized amplitudes resulted in the disappearance of the increased cooling rate caused by electromagnetic vibrations observed at lower frequencies. When particles in the sample have lower electric resistance than the molten sample, these particles are considered to vibrate vigorously in the molten sample by Lorentz force because the electric current concentrates in those. It is suggested that this phenomenon is the reason electromagnetic vibrations decrease the number of crystal nuclei.
It is known that cooling rate from the liquid state is an important factor for producing the bulk metallic glasses. However, almost no other factors such as electric and/or magnetic fields were investigated. The present authors have reported that a new method for producing Mg-Cu-Y bulk metallic glasses by using electromagnetic vibrations is effective in forming the metallic glass phase. However, effects of the electromagnetic vibrations on glass-forming ability in other alloy systems are not investigated. Thus, this study aims to investigate effects of the electromagnetic vibrations on glass-forming ability in Fe-Co-B-Si-Nb bulk metallic glasses. As a result, it was found that glass-forming ability of Fe-Co-B-Si-Nb alloys also enhances with increasing the electromagnetic vibration force. Moreover, the electromagnetic vibrations were found to affect the increase of the cooling rate and the decrease in the number of crystal nuclei directly, but not to affect the crystal growing rate.
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